Alfa, Bravo, Charlie
A voice on a noisy radio channel is easily misunderstood. The letters B, C, D, E, G, P, T and V sound alike, and a wrong letter in a callsign or a runway name can have consequences. Early radio operators used their own lists of words, and several different ones were in use at the same time in different countries and services.
After the Second World War the International Civil Aviation Organization decided to produce a single list, and the work was carried out with linguists, who tested candidate words with speakers of English, French and Spanish. The aim was words that would be clear to all of them. In its present form, the alphabet dates from the 1950s.
The odd spellings
Some words were changed so that people would not mispronounce them. Alfa is spelt with an f so that English speakers do not say it as Al-fa, and Juliett has two t's so that French speakers do not drop the final sound. Numbers have their own pronunciations too, such as niner for nine, to distinguish it from the German nein.
The alphabet has been taken up by police, armed forces and shipping, and is now used far beyond aviation. A pilot spelling a registration letter by letter uses the same words as a person reading out a booking reference over the telephone.